‘‘Twelve days later, nothing. Nothing has changed,’’ the Nevada Democrat said on the Senate floor. ‘‘Sen. Hagel’s exemplary record of service to his country remains untarnished.’’

Reid blamed partisanship over Obama’s choice for the delay. Both Reid and Senate Armed Services Committee Chairman Carl Levin, D-Mich., warned that it was imperative to act just days before automatic, across-the-board budget cuts hit the Pentagon.

Republicans argued that while Hagel served with distinction in Vietnam — Sen. Jim Inhofe called him a ‘‘hero’’ — his record on Israel, Iran and nuclear weapons disqualified him for the top Pentagon job. Last week, 15 Republican senators sent a letter to Obama asking him to withdraw the Hagel nomination.

Sen. Dan Coats, R-Ind., cited Hagel’s at-times halting testimony at his confirmation hearing and his misstatement that the US has a policy of containment toward Iran rather than thwarting Tehran’s nuclear ambitions.

In the course of the rancorous, seven-week nomination fight, Republicans, led by freshman Sen. Ted Cruz and Inhofe, have insinuated that Hagel has a cozy relationship with Iran and received payments for speeches from extreme or radical groups. Those comments have drawn a rebuke from Democrats and some Republicans.

Levin dismissed the ‘‘unfair innuendoes’’ against Hagel and called him an ‘‘outstanding American patriot’’ whose background as an enlisted soldier would send a positive message to the nation’s servicemen and women.

The president got no points with the GOP for tapping the former two-term senator. Republican lawmakers excoriated Hagel, calling him too critical of Israel and too compromising with Iran. They cast the Nebraskan as a radical far out of the mainstream.

Sen. John McCain, R-Ariz., clashed with his onetime friend over his opposition to President George W. Bush’s decision to send an extra 30,000 troops to Iraq in 2007 at a point when the war seemed in danger of being lost. Hagel, who voted to authorize military force in Iraq, later opposed the conflict, comparing it to Vietnam and arguing that it shifted the focus from Afghanistan.

McCain called Hagel unqualified for the Pentagon job even though he once described him as fit for a Cabinet post.

Republicans also challenged Hagel about a May 2012 study that he co-authored for the advocacy group Global Zero, which called for an 80 percent reduction of U.S. nuclear weapons and the eventual elimination of all the world’s nuclear arms.

The group argued that with the Cold War over, the United States could reduce its total nuclear arsenal to 900 without sacrificing security. Currently, the U.S. and Russia have about 5,000 warheads each, either deployed or in reserve. Both countries are on track to reduce their deployed strategic warheads to 1,550 by 2018, the number set in the New START treaty that the Senate ratified in December 2010.

In an echo of the 2012 presidential campaign, Hagel faced an onslaught of criticism by well-funded, Republican-leaning outside groups that labeled the former senator ‘‘anti-Israel’’ and pressured senators to oppose the nomination. The groups ran television and print ads criticizing Hagel.

Opponents were particularly incensed by Hagel’s use of the term ‘‘Jewish lobby’’ to refer to pro-Israel groups. He apologized, saying he should have used another term and should not have said those groups have intimidated members of the Senate into favoring actions contrary to US interests.

The nominee spent weeks reaching out to members of the Senate, meeting individually with lawmakers to address their concerns and seeking to reassure them about his policies.

Hagel’s inconsistent performance during some eight hours of testimony at this confirmation hearing last month undercut his cause, but it wasn’t a fatal blow.

On Feb. 12, a divided Senate Armed Services Committee approved the nomination on a party-line vote of 14-11.

Two days later, a Democratic move to vote on the nomination fell a few votes short as Republicans insisted they needed more time to consider the Hagel pick. The nomination also became entangled in Republican demands for more information about the deadly assault on the US diplomatic mission in Benghazi, Libya last September.

Ambassador Chris Stevens and three other Americans were killed in that attack.